The present disclosure relates to semiconductor memory devices and, more particularly, to a nonvolatile memory device.
Semiconductor memory devices may include volatile memories such as DRAM and/or SRAM. Semiconductor memory devices may also include nonvolatile memories such as EEPROM, FRAM, PRAM, MRAM, flash memory, and the like. A volatile memory may lose data stored therein at power-off, while a nonvolatile memory may retain data stored therein even at power-off. In particular, a flash memory device may have merits such as a high programming speed, low power consumption, a mass storage capacity, and the like. For this reason, a flash memory system including the flash memory device may be widely used as a data storage medium.
The degree of integration of flash memory has generally increased to maintain user's requirements such as superior performance and price competitiveness. However, in view of fabrication processes, a conventional two-dimensional flash memory has a limitation in increasing the degree of integration. A three-dimensional flash memory has been proposed to overcome the limitation.